According the the poet Sarojini Naidu in her poem The Bangle Sellers, there are some particular kinds of bangles that are suitable for the maidens. They are Silver and Blue in colour like the mountain mist. Some of them are ‘flushed’, that is pink and light red in colour like flower buds growing beside a woodland stream. And others are bright like a glowing bloom that divides the transparent beauty of new born green leaves.

Silver and blue coloured bangles are compared to the mountain mist because of the resemblance of colour and also because it symbolizes purity. (Credit: Samrat Dutta)

I think that the colors blue and silver are compared to the mountain mist because they symbolize purity.

They are compared to mountain mist because the Virgin maidens have same longings  as high as the mountains. Also the mountains are very high and seems to touch the  blue sky.. so they are blue as mountain mist.